The present invention relates generally to data transmission between the switching systems of a telecommunication switching network and more particularly to a digital data format arrangement for the exchange of control messages between the peripheral processors of each switching system.
In modern digital telecommunication switching systems a concept of network modularity has been designed allowing the interconnection of small switching systems remote to a larger host system. These remote switching systems have capacities to handle between a few hundred and a few thousand telephone subscribers. The remote switching systems are normally used in areas where the installation of a large switching system would be uneconomical.
A high speed digital data link typically interfaces the host switching system to the remote system through which large amounts of voice and control data are exchanged. The voice data normally comprises subscriber calls switched through either the host or the remote system. The control data may be status exchanges between the host and the remote, i.e. centralized administration, billing and maintenance, or the direct control of the operation of the remote by the host.
The control data exchanges are originated in the sending system peripheral processor transmitted over the high speed digital data link to the receiving system peripheral processor where the data is interpreted. In order to relieve each peripheral processor from the burden of controlling the data link a remote data link controller is implemented in each system which performs all tasks involved in the formatting, transmission and reception of the control data.
The remote data link controllers are connected to each other via digital spans. These digital spans may be T1, T2 or T1C, T3 carriers using DS1, DS2 or DS1C, DS3 data formats, respectively. These digital spans transmit data at high speeds serially at a rate of approximately 1.5-45 megabits per second.
Each data link, in the absence of transmission errors, has the capability of handling upwards of 400 messages per second in each direction. Consequently, the data exchanged should have a format providing excellent error immunity, throughput and enhanced processing performance.
Accordingly, it is the object of the present invention to provide an efficient digital data format arrangement for the exchange of control messages between the peripheral processors of a telecommunications switching network.